Tom Lane wrote:
A more radical way of handling it would be to detect the relevance of an
indexscan in indxpath.c and generate a special kind of Path node; this
would not generalize to other sorts of things as you were hoping, but
I'm unconvinced that the mechanism is going to be very general-purpose
anyway. The major advantage is that this would work conveniently for
comparing the cost of a rewritten query to a non-rewritten one.
I like this point - it makes sense to check that the rewritten query is
less costly to execute than the original!
How are you planning to represent the association between MIN/MAX and
particular index orderings in the system catalogs?
That is the next item to think on, we could have a rewrite catalog that
holds possible transformations for certain functions (certain aggregates
at this stage I guess). This is a bit like Alvaro's idea - however it
may be better to represent it the way he suggested!
regards
Mark
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